The previous chapter presented an overview of how computers communicate over the
Internet, particularly as part of the World Wide Web. It also discussed the functions of
web browsers and servers. While many types of information can be communicated between
browsers and servers, most documents are written using the Hypertext Markup Language
(HTML), which is a primary focus of this chapter.
Actually,HTMLis not a single language, but the name for a family of related languages
that have evolved over the years. We will cover one of the newer members of this family,
XHTML 1.0. In order to fully understand XHTML, you’ll need some familiarity with
another language, the Extensible Markup Language (XML). So we will also cover enough
XML to allow you to understand the formal definition of XHTML 1.0. XML is important in
other contexts as well; additional XML details will be covered in later chapters, particularly